This invention relates generally to absorbent articles used for personal care, such as feminine care articles (e.g., feminine care pads, panty-liners, etc.), diapers, children's training pants, incontinence articles, bandages and the like, and more particularly to such absorbent articles having an absorbent structure that provides for enhanced liquid intake and retention characteristics of such absorbent articles.
Conventional absorbent articles such as feminine care pads typically comprise an absorbent structure disposed between a bodyside liquid-permeable liner and a garment side outer cover, or baffle. The liner and outer cover may extend beyond the absorbent and be bonded together to form a “side edge” or peripheral seal. Some pads further comprise garment attachment panels (e.g., wings or flaps) formed integrally with the liner and/or outer cover and extending laterally outward relative to the intake structure. In use, the pad is placed on the crotch portion of an undergarment such as a panty for taking in and retaining body exudates such as menses, blood and/or urine. The garment attachment panels are folded under and around the crotch portion of the panty and may be secured to each other and/or to the panty crotch portion by suitable adhesive or mechanical fasteners.
The absorbent structure, also sometimes referred to an absorbent body or an absorbent core, may be formed by air-forming, air-laying, co-forming, wet-laying or other known forming technique. For example, the manufacture of such an absorbent structure may begin by fiberizing a fibrous sheet of hydrophilic material in a fiberizer or other shredding or comminuting device to form discrete fibers. In addition, a thermoplastic binder fiber may be mixed with the discrete fibers for subsequent stabilization of the absorbent structure upon heating the binder fibers. In certain absorbent articles, such as training pants and diapers, particles or fibers of superabsorbent materials (also referred to as hydrogel, or hydrocolloid materials), which are water insoluble, water swellable and capable of absorbing at least about ten times their weight in 0.9 weight percent sodium chloride solution in distilled water (saline solution), are also mixed with the fibers. The hydrophilic fibers, binder fibers and (where present) superabsorbent material are then entrained in an air stream and directed to a foraminous forming surface upon which the fibers and superabsorbent material are deposited and accumulated to form the absorbent structure. The absorbent structure may alternatively be a foam, a laminate structure or a combination of layers.
There is a continuing effort by absorbent structure manufacturers to improve the liquid intake performance of absorbent structures as well as the rewet performance thereof. The intake performance refers generally to the ability of the absorbent structure to move fluid through the liner. It is commonly of interest to measure intake with repeated insults thereby measuring the time to absorb as a function of absorbent structure saturation. Rewet generally refers to the ability of the absorbent structure to inhibit previously absorbed liquid against flowing back through the outer surface of the absorbent structure when a compressive load is applied thereto, such as during normal usage including walking, sitting, twisting, etc. The purpose of improving intake performance is to reduce the tendency of the absorbent article to leak during gushes of liquid. A low intake time corresponds with low residence time of liquid on the surface of the product which in turn reduces the likelihood of fluid leakage. Lower rewet corresponds with reduced surface wetness which can improve wearer comfort and helps promote skin health.
However, there is generally considered to be an inverse relationship between the intake performance and the rewet performance of absorbent structures. The reason is generally due to the pore size of the absorbent structure. For example, larger pores allow a faster intake of liquid, but also tend to readily permit flow back of the liquid (rewet) when the absorbent structure is under pressure. Smaller pores more effectively retain liquid, but reduce the rate at which liquid can be taken into the absorbent structure.
There is a need, therefore, for absorbent structures having both improved intake performance and improved rewet performance.